Saturday, April 20, 2024

Mary and John on the Critical Path

In project management school, the lesson on Critical Path includes this rule:
Apply resources first to the critical path, and subordinate demands of other paths to ensure the critical path is never starved.
Beware this hazard: Resources may be real people:
The problem of applying resources arises when we move from the abstract of 'headcount' to the real world of 'Mary' and 'John'. 

Alas! The "resources" are not interchangeable. Mary and John are unique. Consequently, consideration must be given not only to the generic staffing profile for a task but also to the actual capabilities of real people.

Considering Mary and John uniquely
Take a look at the following figure: There are two tasks that are planned in parallel. If not for the unique situation that Mary and John can't be applied to two paths simultaneously, these tasks could be completely simultaneous.

In fact, the critical path could be as short as 50 days -- the length of Task 1. Task 2, as you can see, is only 20 days duration. But for the assignment of Mary and John pushes Task 2 to the right.

But with only Mary and John as resources, the schedule plan stretches out to 65 as shown.

 Here's an idea:
Reorganize the network logic to take into account unique staffing applied to schedule tasks.

Now the schedule plan is shorter, though not as short as it could be if there were resources other than Mary and John. 

And that is actually the embedded lesson learned: With only Mary and John, the two tasks are no longer independent. 

And with a lack of independence, there is a "co-dependency" that is a phenomenon that has to be scheduled also. Thus, we form the rule that interdependency always stretches the plan!

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